Non-Gaussian Random Wave Simulation by Two-Dimensional Fourier Transform and Linear Oscillator Response to Morison Force

[+] Author and Article Information
Xiang Yuan Zheng1

Centre for Ships and Ocean Structures, Norwegian University of Science and Technology, Trondheim 7491, Norwayxiang.y.zheng@ntnu.no

Torgeir Moan

Centre for Ships and Ocean Structures, Norwegian University of Science and Technology, Trondheim 7491, Norwaytormo@ntnu.no

Ser Tong Quek

Civil Engineering Department, National University of Singapore, Singapore 117576, Singaporecveqst@nus.edu.sg


Corresponding author.

J. Offshore Mech. Arct. Eng 129(4), 327-334 (May 02, 2007) (8 pages) doi:10.1115/1.2783888 History: Received October 07, 2006; Revised May 02, 2007

The one-dimensional fast Fourier transform (FFT) has been applied extensively to simulate Gaussian random wave elevations and water particle kinematics. The actual sea elevations/kinematics exhibit non-Gaussian characteristics that can be represented mathematically by a second-order random wave theory. The elevations/kinematics formulations contain frequency sum and difference terms that usually lead to expensive time-domain dynamic analyses of offshore structural responses. This study aims at a direct and efficient two-dimensional FFT algorithm for simulating the frequency sum terms. For the frequency-difference terms, inverse FFT and forward FFT are implemented, respectively, across the two dimensions of the wave interaction matrix. Given specified wave conditions, the statistics of simulated elevations/kinematics compare well with not only the empirical fits but also the analytical solutions based on a modified eigenvalue/eigenvector approach, while the computational effort of simulation is very economical. In addition, the stochastic analyses in both time domain and frequency domain show that, attributable to the second-order nonlinear wave effects, the near-surface Morison force and induced linear oscillator response are more non-Gaussian than those subjected to Gaussian random waves.

Copyright © 2007 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.



Grahic Jump Location
Figure 1

Skewness and kurtosis excess of velocity attenuate with z

Grahic Jump Location
Figure 2

Power spectrum of Morison force (at z=−3m)

Grahic Jump Location
Figure 3

Power spectrum of oscillator displacement




Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In